Book bag



FIG. 1 is a perspective plan view of a book bag showing my new design;

FIG. 2 is a front plan view thereof;

FIG. 3 is a rear view thereof;

FIG. 4 is an elevational view of one side thereof;

FIG. 5 is an elevational view of an opposite side thereof;

FIG. 6 is a top plan view thereof; and,

FIG. 7 is a bottom plan view thereof.

The broken lines in all views indicate stitching and form part of the claimed design. 

The ornamental design for a book bag, as shown and described. 